WO 93/08003 discloses a machine for milling floor areas inside a building for the purpose of leveling, in which machine a device for detecting the height of the floor is provided, this detecting device comprising a laser receiver on the machine, and this laser receiver evaluates an external laser beam which represents the reference height and replaces a reference cord which is otherwise used. According to said document, the height of the rear wheels is adjusted and thus the milling depth is kept at an intended level.
Furthermore, German Patent No. DE 196 32 456 C1 discloses a self-propelled, i.e. driverless, machine for skimming artificial grounds, such as sand tennis courts or the like, in which, for determining the position in connection with markings located on the grounds and thus for the steering, a laser scanner is used which accordingly scans the region in the travel direction in front of the machine with respect to the markings in a horizontal plane and stops the machine if objects which are not envisaged, such as persons, or larger objects are detected in its path.
It is also known in machines for milling traffic areas, so-called “road milling cutters”, to use height regulation in order to set and maintain a certain milling depth for the milling mechanism by adjusting the height of the chassis with respect to a traffic area to be milled.
In addition, in the case of machines for milling traffic areas, there is the problem that persons can move into the hazard region at the side of the machine, in particular at road edges, without being noticed by the driver of the machine.